Hi solidbao,
I did this, yes. I made a second SCSI target on the SCSI2SD card (you can configure this with the 'scsi2sd-util' configuration utility via USB) and copied the A/UX installation CD image onto that virtual SCSI drive. You can even flag the device as being a CDROM, but I don't think I bothered with that.
Copying the image onto the logical unit is the trickiest part. When you configure the second SCSI target on the SCSI2SD, it should say what sector number the logical device starts at. Each block is 512 bytes in size I recall. You can then use 'dd' on your Mac to copy an A/UX installer ISO into that offset in the SD card.
Note the SCSI device offsets are stored in the flash memory on the SCSI2SD device itself, they aren't saved onto the SD card (a design flaw, IMO), so you need to remember that if you swap in any other SD cards in future, you 'll need to change the config agian.
Afterwards, put the SCSI2SD back in and hopefully the Mac will recognise your A/UX install CD and you can then run installation like normal onto a separate SCSI target on the same SCSI2SD card.